Recently, when booting up my laptop it has twice made a nasty abrasive sounding noise. Obviously I was not happy to hear this, but oddly enough after shutting it down and starting it up again, it worked fine and didn't make any odd noises.

I've narrowed the noise down to two potential causes - the fan, or the primary hard drive.

I've run a short and a long SMART test on the drive, both of which reported no errors. I have also mirrored the drive, just in case it suddenly fails. I haven't noticed it making any other bad sounding noises.

Looking at the SMART attributes, there are several which seem like they could be slightly concerning - The Hardware ECC recovered value dropped down to 31 during all the testing and mirroring, although it is climbing back up to its usual value of 50.
Speedfan's online analysis doesn't appear to reveal anything terrible (other than the fact that I should set my laptop to hibernate when I'm not around =P). It does seem to suggest the raw read error rate is worse than other comparable drives though - from what I can tell its either had no errors or two errors (two errors would line up with the fact that its made a noise twice?).

Screenshot of SMART Attributes

Its fairly likely I'll buy a new drive anyway as soon as I can afford it for peace of mind, but it would be nice to know if the drive is definitely having issues and can be returned under warranty.